Baking devices are known for preparing or producing endless strips of a food product, whereby a fluid or pasty dough consisting mainly of flour and water is continuously applied onto a continuously revolving baking surface and there transformed into an endless dried strip through a drying or baking process, this strip being continuously removed from the revolving baking surface.
Such baking devices are equipped with a continuously revolving baking surface carrier heated on its internal and external sides, which carries the revolving baking surface on its external side and transports the same through an external stationary baking zone, at whose beginning a dough application device and at whose end a strip removal device are provided. The dough application device forms an uninterrupted dough strip on the revolving baking surface, which is at least partially baked in the baking zone and at the end of the baking zone is continuously removed from the baking zone by the strip removal device.
In most cases a rotating baking drum is used as the revolving baking surface carrier. The hub of the baking drum is rotatably supported on a horizontally arranged rotation axle. The cylindrical shell of the baking drum is connected with the hub by a support structure and carries the baking surface on its outside. The baking drum surrounds a space containing the support structure and the hub of the baking drum, which also contains the heating device for the heating of the inner drum shell. The baking drum is surrounded by an outer space which contains the dough application device and the strip removal device of the outer stationary baking zone arranged successively in the rotation direction of the baking drum, as well as a heating device for heating the outer surface of the drum shell.
Such baking devices are used for producing baked goods, and for the production of endless wafer strips, which when still warm from baking can be plastically shaped and are further processed in continuously operating production lines to separate objects which in the cooled state are crisp and solid. The endless wafer strips which can be plastically shaped are produced from wafer dough with a high sugar content, which contain 25 to 100% by weight sugar in relation to the flour content of the wafer dough. The objects consisting of sugar-containing wafer dough can represent a final wafer product or an intermediate product in the production of other sweets, e.g. cream-filled wafers or chocolate-coated wafers, candy with fillings, etc. The objects made of plastically shaped sugar-containing endless wafer strips are for instance whole hollow bodies, such as deep cups, wafer rolls, hollow shells, wafer cones, ice cream cones, or also parts of hollow bodies interconnected by layer strips and which together with the layer strips form separate rectangular wafer layers provided with depressions formed by the hollow bodies, or also flat bowls, plates, flat slices, etc.
In the cylindrical baking drums of the known baking devices heat losses result due to the heating of the drum hub and of the support structure form-fittingly connecting the hub with the drum shell. Depending on the construction of the baking drum, the support structure can comprise two radial support plates arranged on the lateral margins of the drum shell, or a single support plate arranged in the middle of the drum shell or at one of its lateral margins.
The heating of the support structure of the baking drum prevents the destruction of the support structure and thereby of the baking drum due to heat stresses, but it produces an uneven heat flow in the drum shell, because the latter is cooled on its outer baking surface by the baked product during the baking process, while the support structure connected to the inside of the drum shell basically maintains an unchanged temperature. This leads to a cambering of the baking surface and to differences of up to 20% in the thickness of the baked endless strip, which have a negative effect on the products made from the respective endless strip. The heating of the support structure also requires heating energy which cannot be used in the baking process. In the production of endless wafer strips which can be plastically shaped in the warm baked stage the operating temperatures range between 200.degree. C. and 250.degree. C.
With the increasing size of the baking drum, increases not only the heat-storing mass of the drum shell, but also the masses of the drum hub and of the support structure, thereby increasing the heat losses of the baking device due to heating of these masses. From WO 95/32630 a baking device for the production of an endless wafer strip which in the warm state can be plastically shaped with a subsequent strip processing device is known. The endless strip is produced on the revolving baking surface carrier of the baking device, which is designed as a revolving baking drum or as a baking strip winding about two guide rollers arranged at a distance from each other. The wafer strip which can be plastically shaped in the warm state is subdivided in a strip processing device into separate fan-shaped wafer pieces, which in a subsequent rolling device are rolled into wafer cones. From Austrian Patent 380 151 a baking device is known for the production of a thin endless wafer strip which in warm state is plastically deformable with a subsequent strip processing device. In the baking device a thin wafer strip is baked on the outside of a revolving one-track baking drum. In the subsequent strip processing device the thin wafer strip is folded, in its longitudinal direction or transversely thereto, into an endless two-layered or multilayered laminated baked strip, which in its plastically deformable state is further processed in another subsequent strip processing device.
EP-A1 0 211 356 describes a baking device for the production of an endless wafer strip plastically deformable in the warm state with a subsequent strip processing device. In the baking device an endless wafer strip is baked on the outside of a revolving baking drum, and in a subsequent strip processing device is subdivided into separate wafer layers, which are then individually processed in the warm, plastically deformable state in a further processing device.
U.S. Pat. No. 3,829,593 a device for the production of an endless pliable strip describes, which immediately after production is rolled into a storage roll. The pliable strip is produced on the outside of a rotating baking drum in a single external baking zone and consists of a dough which is not completely baked on the outer surface of the baking drum. The strip which is pliable in the warm state immediately after production and in the cooled state is intended for the production of dough wraps for Chinese spring rolls, which are stuffed with a precooked filling and are deep-fried in oil until the dough wraps are browned.
DE-OS 24 35 110 describes an installation of the production of prefabricated spring rolls which will be later deep-fried in oil. In this installation on the outside of a revolving baking drum an endless strip of only partially baked dough is produced and this endless strip is fed to a subsequent processing device arranged at a distance, wherein the endless strip is divided into separate square pieces of dough and each piece is made into a prefabricated spring roll. In the processing device a precooked filling mass is put on a dough piece and the dough piece is wrapped around the filling mass to surround it, then rolled up.